Car feels like the tire is slipping....

95 mercury grand marquis. I recently replaced the upper and lower control arm, bushings and ball joint as well as the linkage bar. Now, it feels like the tire is slipping sometimes. Its worse when I turn.

The brake calipers are ok. The driver
side tire has a little wear on the
outside it. And the steering rack, has
started squeaking when I turn the
wheel. The "slipping" feeling comes
from the passenger front tire area.
And it is not all the time just every
once in a while. (You know how it
feels when you ride a bike and turn
the corner, and maybe the front tire
hits a rock or some sand and it feels
like it slips on it, but it's not enough
to make it slide completely and you
fall? That's the slipping feeling I get.)

I have a 2003 grand marquis with 90,000 miles, when I am maintaining a speed I feel a jerking sensation. I thought it might be old spark plugs and an old fuel filter so I changed both of them out. But...